Method and associated apparatus for measuring the adhesiveness of slow-release tablets or the like

ABSTRACT

A method and related apparatus for measuring the adhesiveness of slow-release tablets or the like are disclosed.

[0001] The present invention relates to a method and related apparatus for measuring the adhesiveness of slow-release tablets or the like.

[0002] In particular the method of the invention relates the use of an instrument such as a dynamometer, which is known per se, but used for different types of measurements and which allows accurate and repeatable measurements to be obtained, suitable for determining the coefficient of adhesiveness of the tablets.

[0003] In the pharmaceutical sector, there are active substances that must be assimilated very slowly over time by patients, with the result that a constant, controlled release of those substances must be provided in order to guarantee full efficacy of the substances.

[0004] For this purpose, slow-release tablets have been developed to release the active substances very slowly, for example during the course of a whole night.

[0005] These tablets, in addition to containing active substances intended for “slow release”, may contain also adhesive material which allows the tablets to adhere to the mucous layer of the gums.

[0006] The properties of the adhesive material are activated when hydration occurs, namely, in the case hereunder, when the tablet comes into contact with the salival liquid present in the mouth, which enables the tablet to adhere perfectly to the mucous layer of the gums.

[0007] Since these tablets should remain attached to the gums for a very long period of time, for example overnight, without the risk of becoming detached and being swallowed while a person is sleeping, the pharmaceutical technologist must solve the problem of measuring the adhesive capacity of said tablets.

[0008] To that effect, it is necessary to resort to instruments that can measure the coefficient of adhesion, i.e. the force required to raise and separate a tablet from a surface to which it has been made to adhere, in the most precise possible manner.

[0009] The use of instruments which grip the tablet and detach it from the surface, displacing it in a direction perpendicular to the surface itself, has been proposed.

[0010] However, such a proposal creates various problems, for example, how to grip the tablet firmly or to repeat the measurements with constant parameters, in most cases because the tablet cannot be detached from the surface while keeping perfectly parallel to the latter, thereby giving rise to errors in the measurement recorded.

[0011] The invention aims at overcoming the abovementioned drawbacks arising during measurement of the force needed to detach the tablet from the surface to which it adheres, by acting on the tablet in a direction tangential, rather than perpendicular, to the support surface to which the tablet adheres, namely by applying to the tablet a force which is parallel to the support surface.

[0012] For this purpose a controlled force is applied to the tablet which has been made to adhere to the surface, until the tablet starts to slip, and the force required for the tablet to start to move is measured.

[0013] For this purpose, as mentioned above, the invention envisages using a dynamometer, which is currently being used to measure the hardness of tablets, but has never been used for a purpose similar to that of the invention.

[0014] Since the force needed to cause the separation and displacement of the tablet may be related to the adhesive capacity thereof, such a force may be adopted as a parameter for precise calculation of the adhesiveness.

[0015] The objects and advantages of the invention are achieved by a method for measuring the adhesiveness of slow-release tablets. According to the proposed method, the tablet is placed on the support surface, wetted with a predetermined quantity of water, and subjected to a controlled pressure for a predetermined period of time to promote adhesion. Thereafter, a plunger is allowed to act on the tablet until the latter separates from the surface to which it had been made to adhere.

[0016] The measurement of the force required to displace the tablet can therefore be related to the adhesiveness of the tablet, which can thus be precisely measured.

[0017] Further functions and particular features of the method and the related apparatus for measuring the adhesiveness of slow-release tablets may be better understood from the description which follows, provided herein as a non-limiting example, and reference to the accompanying drawings in which:

[0018]FIG. 1 shows a schematic cross-sectional view, in a vertical plane, of the measuring instrument according to the invention in its entirety;

[0019]FIG. 2 shows a schematic perspective view of the instrument according to the previous figure, with the addition of the compression element.

[0020] With reference to the accompanying figures, FIG. 1 denotes in its entirety an apparatus for measuring the adhesiveness of a tablet, which comprises a support surface 2 on which the tablet 3, whose coefficient of adhesion is to be measured, is placed.

[0021] The support surface 2, which may be displaced horizontally by motor-driven systems (not shown in the figure), is moved in relation to a measuring instrument—denoted by 4—which consists of a plunger opposed to resilient means 5.

[0022] In accordance with the invention, in order to perform measurements under constant conditions, means are envisaged for pressing with a constant force the tablet against the support surface 2, after wetting it with a predetermined quantity of water.

[0023] These means comprise a support element 6 which is positioned astride the tablet support surface 2 and which in turn comprises a guide 7 inside which a calibrated weight 8 slides.

[0024] The support element 6 is positioned with the tubular guide opposite the tablet so that the weight sliding inside the guide rests against the upper side of the tablet 3.

[0025] It should be noted that the tablet 3 surface that rests on the surface 2 is flat, while its opposite side, on which the calibrated weight 8 rests, is convex.

[0026] The method according to the invention comprises the following operating steps:

[0027] the tablet 3 is placed on the support surface 2 of the measuring instrument;

[0028] the tablet 3 is wetted with a predetermined quantity of water supplied in standardised quantity;

[0029] the support element 6 is arranged astride the surface 2 supporting the tablet 3 so that the guide 7 is arranged exactly over the tablet, surrounding it;

[0030] the calibrated weight 8 is introduced into the guide 7 so that it rests on the upper surface of the tablet, and allowed to press the tablet for a predetermined period of time;

[0031] when the adhesive action promoted by the weight 8 has been fully developed, the weight and the associated support element are removed and the surface 2 is pushed against the plunger 4 of the dynamometer, which acts in opposition to resilient means such as a pre-calibrated spring 5.

[0032] The plunger pushes the tablet laterally, causing it advance together with the surface 2 against the force exerted by the spring 5 until the tablet separates from the surface 2 to which it was attached.

[0033] The measurement of the force necessary for causing displacement of the tablet, which depends on the adhesiveness of the tablet itself, may therefore be calculated exactly using parameters and under test conditions which are constant and reproducible, using the known techniques for operation of the instrument.

[0034] As may be noted, the adhesive capacity of the tablet is measured along a tangential plane, namely by applying to the tablet a force which is parallel to the plane to which it adheres, avoiding the difficulties associated with firm gripping of the tablet, separation from the surface and consequent errors in the measurement recorded.

[0035] A person skilled in the art may envisage modifications and variations, thus obtaining solutions which are also to be regarded as included within the scope of protection of the invention hereunder as defined by the following claims. 

1. Method for measuring the adhesiveness of slow-release tablets or the like, comprising the following steps: causing a tablet to adhere to a support surface; applying to the tablet a force which is not perpendicular, but in particular a force which is parallel to said surface; using the measurement of the force necessary for causing separation of the tablet as a parameter for determining the adhesiveness thereof.
 2. Method for measuring the adhesiveness of slow-release tablets or the like as claimed in claim 1, comprising the following steps: placing the tablet on a support surface; wetting the tablet with a predetermined quantity of liquid able to promote adhesion thereof to said surface; arranging, astride the tablet support surface, a support element provided with a guide able to receive a calibrated weight, which is arranged exactly over the tablet; a calibrated weight is introduced into said guide so that it rests on the upper surface of the tablet, exerting a pressure for a predetermined period of time; the weight and the associated support element are removed and the tablet is pushed against a bearing surface which acts in opposition to pre-calibrated resilient means; the force necessary for causing separation of the tablet from the surface to which it was attached is measured.
 3. Method for measuring the adhesiveness of tablets or the like as claimed in the above claims, wherein the apparatus for measuring the adhesiveness of the tablets is a dynamometer.
 4. Method for measuring the adhesiveness of several slow-release tablets or the like as claimed in any one of the above claims, wherein the surface of the tablet (3) in contact with the support surface (2) is flat, while the opposite surface, on which the calibrated weight (8) rests, is convex.
 5. Apparatus for measuring the adhesiveness of tablets or the like using the method as claimed in any one of the above claims, comprising: a sliding support surface (2) on the upper surface of which the tablet, whose coefficient of adhesion is to be measured, is arranged; means able to apply to said tablet a force tangential to said support surface; means able to measure the force necessary for causing separation of the tablet.
 6. Apparatus for measuring the adhesiveness of tablets as claimed in claim 5, wherein said support surface (2) is subject to the action of movement means able to push it towards a bearing surface subject to the action of resilient means so as to press the tablet against said bearing surface, means being envisaged for detecting the force exerted when the tablet is separated from said support surface.
 7. Apparatus for measuring the adhesiveness of tablets as claimed in claim 6, wherein said bearing surface consists of a plunger arranged in opposition to a pre-calibrated spring (5).
 8. Apparatus for measuring the adhesiveness of tablets as claimed in claims 5 to 7, comprising a support element (6) positioned astride the tablet support surface (2), said support element (6) comprising a guide (7) inside which a calibrated weight (8) slides, resting on the upper surface of the tablet (3). 